When performing flaw detection using an ultrasonic probe including multiple transducers aligned in a one direction, each of which is fixed to one another (referred to as an array ultrasonic probe, hereinafter), in transducers (n>m≥1) are selected among n (n≥2) transducers included in the array ultrasonic probe, and the selected transducers transmit ultrasonic waves toward a test material and the selected transducers receive echoes returned from this test material. Echoes received on the respective transducers of the selected transducers are synthesized, and the synthesized waveform is used for the flaw detection on the test material. This procedure is repetitively executed by changing over different units of the selected transducers. Hence, it is important to appropriately evaluate the relative sensitivity of each transducer and appropriately adjust the flaw detection sensitivity of each transducer, which is amplification degree of the echo signal. Specifically, it is important to adjust the flaw detection sensitivity of each transducer such that equal echo intensity is obtained among the respective transducers if each transducer receives an echo from the same artificial flaw.
Such a method for evaluating an array ultrasonic probe is not yet specified by the JIS standard or others at the present time. Hence, it is common to evaluate the performance in compliance with the JIS standard regarding the performance evaluation method, of an immersion normal probe with a single transducer as described in non-Patent Literature 1. Specifically, this method includes a method for evaluation of frequency response using a top surface echo from a flat plate specimen set forth in Section 7.1, a method for evaluation of relative sensitivity using a top surface echo from a flat plate specimen set forth in Section 7.3, and a method for evaluation of beam profile and distance amplitude characteristics using a steel ball with a diameter of ϕ 4 mm or a steel wire with a diameter of ϕ 2.5 mm set forth in Section 8.5.1 of non-Patent Literature 1, respectively.
As mentioned above, flaw detection using an array ultrasonic probe is performed by changing over different units of the selected transducers. Specifically, in performing flaw detection using an array ultrasonic probe, the flaw detection is carried out on each of different units of the selected transducers. As an abnormality diagnosis method for an array ultrasonic probe, such a method has been practiced that carries out flaw detection on a predetermined artificial flaw on every unit of selected transducers, and if the intensity of a resulted synthesized waveform is more than a predetermined allowed value, no abnormality such as malfunction occurs on the transducers of the array ultrasonic probe.